1. Field of the Invention
The invention relates to a packet switching system for transmitting data by using packets, each having a fixed length. More particularly, the invention is concerned with a packet switching system of the type having time division lines, each being associated with a different input and being provided with a time division multiplex channel associated with an output. A selector means associated with a different output for periodically selecting the time division lines. This type of system switches individual packets to desired outputs, by a self-routing technique.
2. Description of Prior Art
A packet switching system switches packets, each comprising data and an address indicative of a destination of the data. In this system, a plurality of packets meant for the same destination often arrive at the same time. Such an occurence may be coped with by combining a sorting circuit network and a routing circuit network such that a conflicting packet is reinputted into the routing circuit network, as taught by Alan Huang et al in an article entitled "A Wideband Digital Switch" published in 1984 in the IEEE Global Telecommunications Conference Record. Another prior art implementation is the use of switch modules, each being associated with a different output for selecting packets which come in via bus type inputs, as disclosed by Y. S. Yeh et al in an article titled "The Knockout Switch: A Simple, Modular Architecture For High-Performance Packet Switching" published in the Proceedings of the IEEE International Switching Symposium 1987.
However, a problem with the sorting and routing network scheme is that a complicated processing is needed to prevent the order of conflicting packets from being inverted in the event of a reinput. Another problem is that a broadcasting function for simultaneously sending out the same data to a plurality of outputs is not readily practicable.
The modular switch scheme has a disadvantage because switches have to be assigned one-to-one at each of the outputs, resulting in large scale of hardware.